engleski

DFT Calculation of NMR CSA Tensors

Density Functional Theory (DFT) calculations were used to quantitatively predict the influence of protein secondary structure elements (phi and psi angles) on NMR chemical shielding anisotropy (CSA) tensors as a prerequisite to structural interpretation of experimental CSA values. The Gaussian98 program package was used employing the 6 311G(d, p) basis set for geometry optimization and 6 311++G(3df, 3pd) basis set for NMR parameters calculation. The Becke's three parameter hybrid functional with the Lee, Yang and Parr correlation functional (B3LYP) was employed in DFT calculation. The gauge independence requirement for NMR parameter calculation was treated with the Gauge Invariant Atomic Orbital (GIAO) approach. The molecular models used in the simulation of protein secondary structure elements and CSA calculations were capped alanine dipeptide, tripeptide and octapeptide. The results of DFT calculations of 1H, 13C and 15N CSA tensors showing dependence on secondary protein structure elements will be demonstrated by way of Ramachandran-CSA diagrams for the dipeptide model. Acknowledgement This work was supported in part by the Austrian Science Fund (FWF) Lise Meitner fellowship (M677), FWF project P15380, Austrian Croatian joint research project 911-02/03-06, and the Ministry of Science and Technology Republic of Croatia project P0098059.

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